Check Engine Light on and Car Stalls

What is your question?

My check engine light has been on for awhile now, and we can't figure out why. It's also had trouble in the past starting after being filled up at the gas station. Recently, this took a dangerous turn when my car completely turned off (battery indicator flashing and all) while I was pulling out of the gas station. Thankfully, there was no traffic at the time, but I hate to think of what could happen next time. We just replaced the battery, so I know that's not the issue. And just the other day, the brake signal flashed and beeped once (just enough to alarm me), then turned off and hasn't turned on since. I have had no issues with my brakes, but my car issues are becoming more alarming than annoying.